adj. Of, relating to, or being the geologic time period between Hadean Time and the Cambrian Period, often subdivided into the Archean and Proterozoic Eras, comprising most of the earth's history and marked by the appearance of primitive forms of life. See Table at geologic time. n. The Precambrian Eon. |
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.